Method of preparing aromatic hydrocarbons from cyclopentadiene compounds



United States PatentO 3,404,191 METHOD OF PREPARING AROMATIC HY- DROCARBONS FROM CYCLOPENTADI- ENE COMPOUNDS Frederick J. Soderquist, Essexville, Harold D. Boyce, Coleman, and Maurice W. Putman, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed Dec. 27, 1966, Ser. No. 604,553 14 Claims. (Cl. 260673) ABSTRACT OF THE DISCLOSURE A process for converting cyclopentadiene hydrocarbons to aromatic hydrocarbons by conducting a mixture of a diluent, such as steam, and cyclopentadiene hydrocarbons through a first reaction zone maintained at a temperature range of from about 250 to 400 C. and conducting the hot efiluent from the first reaction zone through a second reaction zone maintained at about 700 to 900 C. and separating the resultant aromatic hydrocarbons from the hydrocarbon product phase.

BACKGROUND OF THE INVENTION This invention relates to a novel method of preparing aromatic hydrocarbons, useful, for example, as motor fuel blending stock. More specifically the invention involves a method of producing aromatic hydrocarbons, principally benzene and napthalene, directly from cyclopentadiene hydrocarbons.

It is well known that some aromatic hydrocarbons, especially benzene and naphthalene types, are useful as motor fuel blending stock. Also, it is well known that cyclopentadiene hydrocarbons are commonly produced as by-p'roducts in processes involving the carbonization of coke and the cracking of petroleum products. The cyclopentadiene hydrocarbons readily convert to their dimers and co-dimers, i.e., different cyclopentadiene hydrocarbons in polymer form, upon standing because of their reactive nature. The dimers and co-dime'rs are readily reconverted to their monomers upon rnild heating. However, attempts to further process the cyclopentadiene hydrocarbons have, heretofore, resulted in the formation of copious amounts of coke and tars due to their highly unsaturated nature. Therefore, it has been the practice in the industry to pass streams containing cyclopentadiene hydrocarbons through a mild hydrogenation step to convert them to less reactive cyclo-olefins and cyclo-parafiins. Following such treatment the cyclo-olefins and cycloparafiins may be further processed to form blending stocks for motor fuels.

SUMMARY OF THE INVENTION By utilizing the techniques of the present invention, it is now possible to convert cyclopentadiene hydrocarbons directly to highly stable aromatic hydrocarbons which make superior motor fuel blending stocks. The operation of the present process permits the separation and recovery of pure aromatic hydrocarbons by conventional separation methods.

. 3,404,191 Patented Oct. 1, 1968 ice - It is a principal object of the present invention to produce highly stable aromatic hydrocarbons directly from cyclopentadiene hydrocarbons readily obtained as byproducts from the cracking of petroleum products and from the carbonization of coke.

The invention, as well as additional objects and advantages thereof, will be readily apparent from a reading of the detailed description presented hereinafter.

The term space velocity as used herein designates grams of cyclopentadiene hydrocarbons per unit volume of reaction zone, in milliliters, per hour.

Cyclopentadiene hydrocarbons a herein employed designates monomeric cyclopentadiene and substituted cyclopentadienes, dimers and co-dimers of cyclopentadiene and substituted cyclopentadienes and mixtures thereof, wherein the substituted cyclopentadiene hydrocarbons correspond to the formula wherein each R individually represents H or a hydrocarbon group derived from an *alkane, olefin, diolefin, or acetylene hydrocarbon containing from 1 to 12, inclusive, carbon atoms, and where n is an integer ranging from 1 to 5.

In accordance with the present invention, usually a mixture of at least one cyclopentadiene hydrocarbon and a diluent is first mildly heated in a first reaction zone maintained atabout 250 C. to 400 C. to convert any dimers or co-dimers to the corresponding cyclopentadiene monomers. The hot vapor efliuent therefrom, containing the diluent and the monomeric cyclopentadiene hydrocarbons, is conducted through a second reaction zone which is maintained at an elevated temperature of from about 700 to 900 C. whereupon'the cyclopentadiene hydrocarbons are converted to highly stable aromatic hydrocarbons. The aromatic hydrocarbons are separated from the product hydrocarbon phase by such standard techniques as distillation, crystallization, or absorption, and unreacted cyclopentadiene hydrocarbons are generally recycled through the process. The first low temperature reaction zone may be bypassed if monomeric cyclopentadiene hydrocarbons are available as feed stock. It has been discovered in accordance with this invention that the diluent present efiiciently prevents the formation of tars and carbonaceous material which have heretofore been associated with high temperature treatment of cyclopentadiene hydrocarbons.

DESCRIPTION OF THE PREFERRED EMBODIMENT In practice one or more cyclopentadiene hydrocarbons are passed through a reaction zone maintained at about 250 to 400 C. concurrently with a substantially equal weight of a gaseous diluent which is substantially inert tion zone should preferably be packed with an inert material such -as--Raschig--rings,- Berl saddles, or-the like packing materials which promote reactant contact and distribution.

The hot vapor elfiuent from the first reaction zone is conducted through a second reaction zone heated to a temperature of from about 700 to 900 C., at a sulficient fiow rate to assure a substantially complete conversion of the cyclopentadiene hydrocarbons to aromatic hydrocarbons. In the second zone the desired conversion of cyclopentadiene hydrocarbons to aromatic hydrocarbons occurs. When a source of monomeric cyclopentadiene compounds is available, they need only be conducted through the second reaction zone with the requisite quantity of diluent as set forth herein and at the designated space velocity and temperature ranges to convert them to aromatic hydrocarbons.

The effiuent vapors from the second reaction zone are cooled and condensed and the aromatic hydrocarbons produced are isolated from the product hydrocarbon phase by conventional separation methods; unreacted cyclopentadiene hydrocarbons generally are recycled through the process steps.

The process as described herein is normally run at atmospheric pressure but it can be carried out at higher or lower pressures.

The reaction zone temperatures can be varied within designated ranges, as indicated. It has been observed, however, that the most efiicient conversion of the dimers and co-dimers to their monomers is achieved by maintaining the first reaction zone at about 400 C. The second reaction zone ordinarily is maintained within a range of from about 700 to 900 C. The system is less efiicient at temperatures lower than about 700 C. in the second reaction zone and greater proportions of cyclopentadiene hydrocarbons must be recycled through the process. Temperatures greater than about 900 C. cause degradation of the cyclopentadiene hydrocarbons and of the aromatic hydrocarbons produced. The most favora ble temperature associated with the second reaction zone is about 850 C.

The flow rate, defined as a space velocity of the cyclopentadiene hydrocarbons, varies in accordance with the respective dimensions of the two reaction zones. It has been found that a space velocity of from about 0.1 to 2L0 grams cyclopentadiene hydrocarbons per milliliter reactor volume per hour is operable. A space velocity of approximately 0.6 gm./ml./hr. is preferred. Lower space velocities cause plugging of the reaction apparatus while higher velocities produce a less efficient yield rate.

The presence of a diluent is necessary to avoid carbonization and tar formation. Examples of suitable diluents are steam, nitrogen, carbon dioxide, argon, aliphatic hydrocarbons, aromatic hydrocarbons, and the like which are substantially inert to the reactants and reactant products during operation of the process. The proportion of diluent to initial cyclopentadiene hydrocarbons is expressed in the weight of diluent to the weight of feed stock. A proportion of one to one has been observed to produced the maximum economical limit but higher ratios are operable. Proportions of lower than 1:1 can be used, however, proportions lower than 0.2:1 cause excessive plugging. A proportion of from about 0.5 :1, to

about 1:1 is preferred in the actual operation of the process. 1 a

The cyclopentadiene hydrocarbon feed stock can consist of substantially pure monomeric cyclopentadiene hydrocarbons or products from petroleum cracking and from the carbonization of coke after distilling olf the heavier products may be used. For example, debutanizer bottoms have been utilized as starting feed stocks in the actual operation of the present invention. When the feed stock consists principally of monomeric cyclopentadienes they need only be conducted through the second reaction zone at the conditions indicated herein.

As indicated, both cyclopentadiene and substituted cyclopentadiene hydrocarbons are operable as initial feed stocks. Dicyclopentadiene and methylcyclopentadiene have been used as feed stocks. Other substituted cyclopentadiene hydrocarbons are advantageously used, such as, for example, 2-hexyl-rnethylcyclopentadiene, l-ethenyl- 3-octa-dicyclopentadiene, 1-pentyl-4-octenyl-dicyclopentadiene, 1-methyl-3-propylacetylenedicyclopentadiene.

Benzene, naphthalene and toluene are the principal aromatics produced in the operation of the P esent invention along with indene and minor amounts of other substituted aromatic hydrocarbons.

The method of the present invention can be run as a continuous operation with a means for recycling unreacted cyclopentadiene hydrocarbon or as a batch-type operation, and as indicated the first reaction zone is not required when the feed stock consists primarily of monomeric cyclopentadiene hydrocarbons.

The following examples further illustrate the utility and operation of the present invention. They are included herein to aid in understanding the present invention and are not meant to limit the scope of the invention to the specific examples enumerated.

Example 1 An apparatus was set up in which a vertical two-zone reactor was mounted in two electric furnaces for temperature control. The reactor consisted of a section of A-inch schedule 40, type 446, stainless steel pipe. The upper zone was packed with Mr inch Berl saddles, and maintained at about 380 C. The lower zone was the remainder of the open tube and its temperature was adjusted in a stepwise fashion from 700 to 900 C. in 50 C. steps. Dicyclopentadiene and a substantially equal weight of water were fed continuously to the upper zone of the reactor at a rate of 50.9 and 50.1 grams per hour respectively or, as expressed in space velocity, 0.582 gram dicyclopentadiene per milliliter reactor volume per hour.

Effiuent vapors from the lower reaction zone were conducted to a conventional water-cooled condensing and receiving apparatus and non-condensible gases were continuously metered and then vented. Representative liquid and gaseous samples were taken at each temperature level of the second reaction zone and analyzed by infrared and mass spectrographic techniques. The quantities of specific aromatics produced in both the gaseous and liquid phases were calculated from the analyses and are tabulated in following Table I. Approximately 14 to pounds Of total aromatics per 100 pounds of dicyclopentadiene feed were made, depending on the operating temperatures employed. The major aromatics produced were the more desirable benzene and naphthalene.

TABLE I Oper- Percent; Lbs. liquid phase recovered per 100' lbs. feed stock Gas phase Total ating liquid aromatics, Feed stock temp recovery Naphtliaa-Metliyl fl-Methyl lbs/100 lbs.

C. Benzene Toluene Styrene Indene lene naphtha- 'naphtha- Benzene Toluene feed stock lene lene Dicyclopentadiene 700 95. 6.22 3.83 13 88 750 83. 55 6. 27 12. 53 32 20 800 76. 21 6. 10 22.86 50 83 850 82.58 0. 61 2s. 65 17 900 78. 46 4. 71 29. 81 53130 3,404,191 6 Example 2 I aromatic hydrocarbons and unreacted cyclopentadieuc hydrocarbons.

3. Tlieprocess as defined in claim 1 and including the additional step of recycling unreacted cyclopentadiene 5 hydrocarbons through said sequential reaction zones at saidflow rate and temperature ranges. Y

4. The process as defined in claim 1 wherein the cyclopentadiene hydrocarbon is a member of the group consisting of monomeric cyclopentadiene and substituted cyclopentadienes; dimers and co-dimers of said cyclopen- The process described in Example 1 was repeated using methyl cyclopentadiene dimer as the feed stock. Flow rates, temperatures, space velocities, and proportions were essentially identical to those employedin Example 1. The calculated yieldsgof; aromatic hydrocarbons are presented in following Table IIjApproxirnately, 30. to 57..pounds of,aromati cs were produced per 100 pounds of methyl cyclopent'adiene'fecd stock and benzene and naphthalene were the major constituents.

, TABLE II Oper- Percent Lbs. liquid phase recovered per 100 lbs. feed stock Gas phase Total ating liquid aromatic, Feed stock temp, recovery N aphthaa-Methyl B-Methyl lbs/100 lbs.

C. Benzene Toluene Styrene Indene lene naphthanaphtha- Benzene Toluene feed stock lene lene Methyl 700 88. 96 20. 02 5. 34 1. 78 2. 67 0.31 0. 03 30. cyclopentadiene 750 80. 20. 49 7. 63 4. 42 9. 64 1.21 4 1. 70 0. 01 49. 12 dimer 800 78.82 20. 49 6. 70 5.12 14. 58 1.18 4 73 2. 94 0.02 55. 76 850 78. 22 20. 34 5. 87 4. 30 16. 04 1; 17 5 08 4. 52 0.08 57. 900 71. 34 17. 12 3. 92 2. 50 13. 91 0. 71 9. 14 0. 22 50. 44

Example 3 tadiene and substituted cyclopentadienes and mixtures thereof, and where said substituted cyclopentadiene hy- E l A duplicate of xamp e 1 was run using cyclopentane 25 drocarbons correspond to the formula as the feed stock. Conditions and procedures were essentially the same as in Example 1. The aromatic yields are listed in Table III. Approximately /3 the yield of the process of Example 1 was realized and then only at high temperature levels. 30

TABLE III Oper- Percent Lbs. liquid phase recovered per 100 lbs. feed stock Gas phase Total ating liquid aromatic, Feed stock ternp., recovery Naphthaa-Methyl B-Methyl lbs/100 lbs C. Benzene Toluene Styrene Indene lene naphthanaphtha- Benzene Toluene feedstock lene lene Cyclopentadiene. 700 89. 95 0. 02 0.92 750 54.09 0 0a 2.24 800 18.81 1 07 0.09 14.43 850 23. 04 3 05 0. 2a 22 99 900 36. a7 4 72 0. 30 27 9a In accordance with the process as heretofore described, wherein each R individually represents H or a hydrocarby-products from petroleum cracking processes, namely bon group derived from an alkane, olefin, diolefin and cyclopentadiene hydrocarbons, can readily be converted acetylene hydrocarbon containing from 1 to 12, inclusive, to highly desirable aromatic hydrocarbons useful, for carbon atoms, and where n is an integer ranging from example, as motor fuel blending stocks. In accordance 1 to 5. with the actual operation of the present invention the 5. The process as defined in claim 1 wherein the proby-products can be converted more readily and more portion of diluent to cyclopentadiene hydrocarbons is economically than heretofore possible. wihin the range of from about 0.2:1 to about 1:1 by

Various modifications of the invention can be made i ht, p l departing m 13 P- thereof, 6. The process as defined in claim 1 wherein the flow -=f0r 1t 5 Understood t We llmlt Ourselves y as derate of said mixture through said reaction zones is mainfined 1n the appended clalms. tained within the range of about 0.1 to about 2.0 grams Ola-1m! of cyclopentadiene hydrocarbon per milliliter of reaction 1. A process for converting cyclopentadiene hydro- Zone per houn carbons t0 flrqmatlc hydl'oflafbons P 7. The process as defined in claim 1 wherein the diluent (a) sequentially conductlng a mixture of at least one i Steam, I

y l p f Y f and a gaseous dlluent 8. A process for converting monomeric cyclopentadiene Whlch 1S Substamlany men I the a and hydrocarbons to aromatic hydrocarbons comprising: actant products at the reactlon conditions through a (a) conducting a mixtum of at least one monomeric first reaction zone mam.a1ned at a temperature within cyclopentadlene hydrocarbon and a gaseous dlluent the range of about 250 C. to about 400 C. at a flow rate sufficient to assure a substantially complete conversion of dimers and co-dimers of said cyclopentadiene hydrocarbons to the corresponding monomers; and

(b) conducting the efiluent from the first reaction zone through a second reaction zone maintained at a temwhich is substantially inert to the reactants and reactant products at the reaction conditions through a reaction zone maintained at a temperature within the range of about 700 C. to about 900 C. at a flow rate sufficient to assure a conversion of the cyclopentadiene hydrocarbons to aromatic hydrocarbons.

para/[um within the range f about 700" Q to about 9. The process as defined in claim 8 and including the 900 C at a flow rate suflicient to assum a onver. additional step of condensing the efiluent gases evolved sion of the cyclopcntadiene hydrocarbons to arofrom said reaction zone and separating therefrom aromatic hydrocarbons. matic hydrocarbons and unreacted cyclopentadiene hy- 2. The process as defined in claim 1 and including the drocarbons. additional step of condensing the effluent gases evolved 10. The process as defined in claim 8 and including the from the second reaction zone and separating therefrom 7 additional step of recycling unreacted cyclopentadiene hydrocarbons through said reaction zone at said flow rate and temperature ranges. M

11. The process as defined in claim 8, wherein the monomeric cyclopentadiene hydrocarbon is a member oi the group consisting of cyclopentadiene, substituted cyclopentadiene and mixtures thereof and where saidflsubstituted cyclopentadiene hydrocarbons correspond to -the formula il portion of the diluent to the cyclopentadiene hydrocarbon is within the range of from about 0.2:1 to about 1:1 by wei ht, p I 13. The process as defined in claim 8 wherein the flow 'rate'of said mixture through said'reaction zones is maintained Within the range of about 0.1 to about 2.0 grams of cyclopentadiene hydrocarbon per milliliter of reaction 'zone per hour. 1

l 14. The process as defined in claim 8 wherein the diluent is steam. v I i DELBERT E. GANTZ, PrimaryExaminer.

C. R. DAVIS, Assistant Examiner; 

